MOIC —  Invited Talk in Monday-C   (01-Oct-12   14:15—15:00)
Electron Beam Diagnostic System for the Japanese XFEL, SACLA
  • H. Maesaka, H. Ego, C. Kondo, T. Ohshima, Y. Otake, H. Tomizawa
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • S. Matsubara, T. Matsumoto, K. Yanagida
    JASRI/SPring-8, Hyogo, Japan
  An x-ray free-electron laser (XFEL) based on self-amplified spontaneous emission (SASE) requires a highly brilliant electron beam. The Japanese XFEL facility, SACLA, requires a normalized emittance less than 1 mm mrad and a peak current more than 3 kA. To achieve this high peak current, 1 A beam with 1 ns duration from a thermionic electron gun is compressed down to 30 fs by means of a multi-stage bunch compressor system. Therefore, the beam diagnostic system for SACLA was designed for the measurements of the emittance and bunch length at each compression stage. We developed a high-resolution transverse profile monitor and a temporal bunch structure measurement system with a C-band rf deflector cavity etc. In addition, precise overlapping between an electron beam and radiated x-rays in the undulator section is necessary to ensure the XFEL interaction. Therefore, we employed a C-band sub-micron resolution RF-BPM to fulfill the demanded accuracy of 4 um. The beam diagnostic system surely contributed to the first x-ray lasing at a wavelength of 1.2 Angstrom. We present a design strategy of the whole beam diagnostic system and the achieved performance for each monitor.